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pkg/dev_compiler/tool/input_sdk/lib/collection/linked_hash_set.dart

-// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-part of dart.collection;
-
-/**
- * A [LinkedHashSet] is a hash-table based [Set] implementation.
- *
- * The `LinkedHashSet` also keep track of the order that elements were inserted
- * in, and iteration happens in first-to-last insertion order.
- *
- * The elements of a `LinkedHashSet` must have consistent [Object.operator==]
- * and [Object.hashCode] implementations. This means that the `==` operator
- * must define a stable equivalence relation on the elements (reflexive,
- * symmetric, transitive, and consistent over time), and that `hashCode`
- * must be the same for objects that are considered equal by `==`.
- *
- * The set allows `null` as an element.
- *
- * Iteration of elements is done in element insertion order.
- * An element that was added after another will occur later in the iteration.
- * Adding an element that is already in the set
- * does not change its position in the iteration order,
- * but removing an element and adding it again,
- * will make it the last element of an iteration.
- *
- * Most simple operations on `HashSet` are done in (potentially amortized)
- * constant time: [add], [contains], [remove], and [length], provided the hash
- * codes of objects are well distributed..
- */
-abstract class LinkedHashSet<E> implements HashSet<E> {
-  /**
-   * Create an insertion-ordered hash set using the provided
-   * [equals] and [hashCode].
-   *
-   * The provided [equals] must define a stable equivalence relation, and
-   * [hashCode] must be consistent with [equals]. If the [equals] or [hashCode]
-   * methods won't work on all objects, but only on some instances of E, the
-   * [isValidKey] predicate can be used to restrict the keys that the functions
-   * are applied to.
-   * Any key for which [isValidKey] returns false is automatically assumed
-   * to not be in the set when asking `contains`.
-   *
-   * If [equals] or [hashCode] are omitted, the set uses
-   * the elements' intrinsic [Object.operator==] and [Object.hashCode],
-   * and [isValidKey] is ignored since these operations are assumed
-   * to work on all objects.
-   *
-   * If you supply one of [equals] and [hashCode],
-   * you should generally also to supply the other.
-   *
-   * If the supplied `equals` or `hashCode` functions won't work on all [E]
-   * objects, and the map will be used in a setting where a non-`E` object
-   * is passed to, e.g., `contains`, then the [isValidKey] function should
-   * also be supplied.
-   *
-   * If [isValidKey] is omitted, it defaults to testing if the object is an
-   * [E] instance. That means that:
-   *
-   *     new LinkedHashSet<int>(equals: (int e1, int e2) => (e1 - e2) % 5 == 0,
-   *                            hashCode: (int e) => e % 5)
-   *
-   * does not need an `isValidKey` argument, because it defaults to only
-   * accepting `int` values which are accepted by both `equals` and `hashCode`.
-   *
-   * If neither `equals`, `hashCode`, nor `isValidKey` is provided,
-   * the default `isValidKey` instead accepts all values.
-   * The default equality and hashcode operations are assumed to work on all
-   * objects.
-   *
-   * Likewise, if `equals` is [identical], `hashCode` is [identityHashCode]
-   * and `isValidKey` is omitted, the resulting set is identity based,
-   * and the `isValidKey` defaults to accepting all keys.
-   * Such a map can be created directly using [LinkedHashSet.identity].
-   */
-  external factory LinkedHashSet({bool equals(E e1, E e2),
-                                  int hashCode(E e),
-                                  bool isValidKey(Object potentialKey)});
-
-  /**
-   * Creates an insertion-ordered identity-based set.
-   *
-   * Effectively a shorthand for:
-   *
-   *     new LinkedHashSet(equals: identical,
-   *                       hashCode: identityHashCode)
-   */
-  external factory LinkedHashSet.identity();
-
-  /**
-   * Create a linked hash set containing all [elements].
-   *
-   * Creates a linked hash set as by `new LinkedHashSet<E>()` and adds each
-   * element of`elements` to this set in the order they are iterated.
-   *
-   * All the [elements] should be assignable to [E].
-   * The `elements` iterable itself may have any element type,
-   * so this constructor can be used to down-cast a `Set`, for example as:
-   *
-   *     Set<SuperType> superSet = ...;
-   *     Iterable<SuperType> tmp = superSet.where((e) => e is SubType);
-   *     Set<SubType> subSet = new LinkedHashSet<SubType>.from(tmp);
-   */
-  factory LinkedHashSet.from(Iterable elements) {
-    LinkedHashSet<E> result = new LinkedHashSet<E>();
-    for (final element in elements) {
-      E e = element as Object/*=E*/;
-      result.add(e);
-    }
-    return result;
-  }
-
-  /**
-   * Executes a function on each element of the set.
-   *
-   * The elements are iterated in insertion order.
-   */
-  void forEach(void action(E element));
-
-  /**
-   * Provides an iterator that iterates over the elements in insertion order.
-   */
-  Iterator<E> get iterator;
-}